1. Field of the Invention
This invention relates to carrier mounted, material handling equipment, such as cranes and excavators, and more specifically, it pertains to an operator's cab mounting on such equipment.
2. Description of the Prior Art
United States Pat. No. 2,529,200 discloses a material handling machine with an operator's cab mounted upon a front corner of a machinery platform that rotates in a generally horizontal plane. The cab is fixed in a stationary position on the platform, relative to an adjacent machinery enclosure, and extends to a higher level than the enclosure to provide an unobstructed view in all directions for the operator. Specialized loading operations often require an operator to sit at an elevated vantage point in order to have an unrestricted view of the work he is performing or else have a spotter to act as a second pair of eyes and to give signals as to what the operator should do. Such operations include loading or unloading material within a railroad gondola car and loading or unloading material upon an elevated pile, such as logs stacked high on a truck.
U.S. Pat. Nos. 3,431,016 and 3,630,398 disclose elevated cabs that can be pivoted about a horizontal axis to reduce the profile of a vehicle for travel clearance requirements. U.S. Pat. No. 3,545,633 discloses an elevated cab that can be collapsed for highway travel to avoid interference with bridges and other overhead obstructions. Thus, while it is desirable to have an elevated cab on material handling equipment that provides the operator with an unobstructed view for operation of the equipment, it is also necessary to maintain the equipment profile within limits for clearance when traveling.
An operator's cab for carrier mounted cranes and excavators is normally mounted upon a machinery platform that rotates in a generally horizontal plane about a substantially vertical axis. The cab is offset to one side from the vertical axis of rotation because a lifting boom and its associated machinery are normally located thereon but the cab does face toward the forward end of the boom and turns therewith to various work positions so that the operator faces the work. Thus, the cab is mounted for one degree of movement relative to the carrier but there remains the need to have the cab elevated for visibility during operation and lowered for clearance when traveling. When the cab is mounted in a stationary elevated position, the operator must climb a high ladder or adjacent structure to gain access to the cab. Such stationary structure makes it difficult to find access to adjacent machinery for repairs.